如图，网孔电流法，左边网孔，顺时针绕行：
9 * I1 - 4 * 2 = 10
I1 = 2A
Uab = - 5 * 2 + 10 - 3 * 2 = -6V
Rab = 5 + 3//6 + 3 = 10Ω
I = -6 / 10 = - 0.6A
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15.5 串联电路中电流的规律
